rMWd6a3b6cfa8f5: TempUser EditPage and permissions added a new named user group to differentiate between temporary users (who where also part of user) and regular users. rMW83dbe59d57f4: Suppress "named" group when TempUser system is disabled made that group conditional on the wiki having temp users, due to UI concerns (as users' membership in named was shown on various public interfaces). rMWdd2f898f86ee: Add temporary users to a 'temp' group, and stop adding them to 'user' removed temporary users from the user group and created a temp group for them instead, to make the default permissions for temporary users more like anonymous users.

So now we have a named group which includes exactly the same users that user also includes, except it might or might not exist depending on wiki configuration. There isn't any point to it.

See also T340457: In UserGroupManager::getUserImplicitGroups, add temporary users to a 'temp' group instead of the 'user' group:

Currently, temp users are added to the 'user' group, along with users who create an account. Users who create an account are also added to a 'named' group. If we kept the status quo, then communities would have to actively remove rights from the 'user' group if they didn't want temp users to have them, and give those rights to the 'named' group instead.

We're instead going to introduce a 'temp' user group. Temporary users will be added to the 'temp' group instead of the 'user' group, meaning that if communities do nothing (change no configuration), temp users will not have any more rights than are assigned to the '*' group. Communities must actively give them rights by assigning rights to the 'temp' group.

(We still keep the 'named' group, in case a future product decision is taken to assign temporary users to the 'user' group.)